Conventionally, contamination and infections due to needle-stick injuries with injection needles or puncture needles have been a problem in medical facilities. In particular recently, as hepatitis B, hepatitis C and HIV (human immunodeficiency virus) have become widespread throughout the population, there is a strong demand for means that actively prevent accidental needle-stick injuries.
As a means for preventing needle-stick injuries, various injection needle devices have been proposed, in which the cannula is covered by a cover when collecting injection needles or puncture needles after use. Most of such means for reduction of needle-stick injuries have a cylindrical protection cover (referred to as “shield” in the following) for preventing needle-stick injuries after use, and this shield can slide with respect to the injection needle. That is to say, depending on the sliding state of the shield, the injection needle is either exposed or it is covered by the shield.
On the other hand, for measures such as the infusions or blood transfusions, or extracorporeal blood circulation, winged infusion needle devices are used widely. Winged infusion needle devices have a structure in which wings are mounted on a hub, in which the infusion needle is fixed at the front, and whose rear is connected to an infusion tube. Thus, the means for preventing needle-stick injuries with a winged injection needle device necessitates a special structure. That is to say, the structure has to be such that the wings do not obstruct the sliding of the shield. For this reason, conventional structures are classified into types in which the wings are attached to the infusion needle or the hub and types in which the wings are attached to the shield.
Examples of the latter structure are described for example in JP H06-7861B, WO 91/04761 or U.S. Pat. No. 5,088,982, In these conventional examples, the wings are attached to the outer peripheral surface of a slidable tubular shield, and the wings slide together with the shield on the outer side of the infusion needle. In order to prevent needle-stick injuries after use of the infusion needle, the tip of the infusion needle can be covered by sliding the shield.
In the course of using such an infusion needle device in which wings are attached to the shield, a mechanism is necessary for holding the infusion needle temporarily at a predetermined position with respect to the shield and fitting the two together. Furthermore, it is desirable that the effect of holding the needle with respect to the shield differs during the puncturing action and during the storage action of storing the injection needle in the shield for the sake of preventing needle-stick injuries, as described below.
When performing a puncturing action, the shield is grasped to perform the action, so that it is necessary that the needle is held securely by the shield. On the other hand, when performing the action of storing the needle away, the force for holding the shield should be rather weak in order to make easy the operation therefore. When the holding force is too strong, then the action of sliding the needle within the shield becomes difficult, and there is the risk that it may lead to unexpected accidents. On the other hand, when the needle is retained on the patient, the shield is fastened to the patient's skin near the punctured portion, so that if the needle is easily moved within the shield in this situation, there is the risk that the needle is easily pulled out from the patient. Consequently, it is inconvenient if the holding force is too weak during needle retention. In conclusion, it is preferable that after the puncturing action, a suitable holding force weaker than that at the time of the puncturing action acts on the injection needle or the hub.
However, in conventional injection needle devices having a winged shield, the holding of the injection needle at the time of the puncturing action and after the puncturing action (i.e. during retention and during removal of the needle) is performed by the same mechanism, and a suitable holding force could not be attained for both the puncturing action and the storing action.
Consequently, it is an object of the present invention to provide a medical needle device, in which both during the puncturing action and after the puncturing action, the medical needle can be held with optimum holding power with respect to a winged shield, and with which the action of storing the medical needle into the shield after use can be performed safely and easily.